The present invention relates to an inherently tacky polymeric microspheres which are solvent-dispersible, solvent-insoluble and elastomeric in nature. In particular, this invention relates to said tacky polymeric microspheres which are prepared employing a non-ionic suspension polymerization system.
In U.S. Pat. No. 3,691,140 to Silver, there are disclosed inherently tacky acrylate copolymer microspheres comprising a major portion of at least one alkyl acrylate ester and a minor portion of an ionic monomer. As discussed in Silver the microspheres are prepared utilizing en emulsifier in an amount greater than the critical micelle concentration in the absence of an externally added protective colloid or the like. As such is the case, the ionic comonomer is considered an essential component of the microspheres described therein.
In U.S. Pat. No. 4,266,152 to Baker et al, polymeric microspheres are disclosed wherein said microspheres are formed from non-ionic monomers by suspension polymerization techniques in the presence of ionic suspension stabilizers. Typically, such microspheres are homopolymers and do not contain an ionic comonomer.
U.S. Pat. No. 4,495,318 to Howard discloses inherently tacky polymeric microspheres of a type very similar as those disclosed in the Baker et al patent mentioned above, however, said microspheres are prepared by suspension polymerization techniques utilizing ionic suspension stabilizers and a non-ionic emulsifiers.
A second U.S. Patent to Howard, U.S. Pat. No. 4,598,112 discloses the same type of microsphere as described in his earlier patent except that said microspheres are prepared by suspension polymerization techniques utilizing an ionic stabilizer and a cationic emulsifier.
As is clear from the above noted prior art, polymeric microspheres of the type disclosed required the presence of an internal or external ionic suspension stabilizer means, i.e., either an ionic monomer in a copolymer system or an ionic suspension stabilizer in the absence of an ionic monomer.
It has now been found, that inherently tacky polymeric microspheres which are infuseable, solvent dispersible and solvent insoluble can be prepared using suspension polymerization techniques in the presence of a non-ionic stabilizer and a non-ionic emulsifier.